Multi-chip touch screens

TECHNICAL FIELD

p-0002The subject matter discussed herein relates to touch screen technologies, for example, to techniques for combining measuring devices, e.g. on multiple chips, for use with larger touch screens such as may have an arrangement of multiple touch screens or areas forming a large touch screen.

BACKGROUND

p-0003A position sensor is a device that can detect the presence and location of a touch, by a user's finger or by an object, such as a stylus, for example, within a display area of the position sensor display screen. In a touch sensitive display application, the position sensor enables a user to interact directly with what is displayed on the screen, rather than indirectly with a mouse or touchpad. Position sensors can be attached to or provided as part of computers, personal digital assistants (PDA), satellite navigation devices, mobile telephones, portable media players, portable game consoles, public information kiosks, and point of sale systems etc. Position sensors have also been used as control panels on various appliances.

p-0004There are a number of different types of position sensors/touch screens, such as resistive touch screens, surface acoustic wave touch screens, capacitive touch screens etc. A capacitive touch screen, for example, may include an insulator, coated with a transparent conductor in a particular pattern. When an object, such as a user's finger or a stylus, touches or is provided in close proximity to the surface of the screen there is a change in capacitance. This change in capacitance is sent to a controller for processing to determine the position of the touch.

p-0005An array of drive (in one example X) electrodes or lines and sense (in this example Y) electrodes or lines, of conductive material, can be used to form a touch screen having a plurality of nodes. A node is formed at each intersection of X and Y electrodes. Although referred to as an intersection, the electrodes cross but do not make electrical contact. Instead, the sense electrodes are capacitively coupled with the drive electrodes at the intersection nodes. Applying a voltage across the array of electrodes creates a grid of capacitors. When an object touches (contacts or comes in close proximity to) the surface of the screen, the capacitance change at every individual point on the grid can be measured to determine the location or position of the touch.

p-0006In recent years, it has become desirable for touch sensitive position sensors to be used in large screens. As touch screen size grows, the number of capacitive sensing nodes contained in a touch screen increases. To measure capacitance at more nodes on a screen requires increased measurement device capacity, either in the form of more complex measurement devices or chips or in the form of more measurement devices, to handle all the nodes of the larger screen size. A screen of four times the node count as could be handled by a particular size/capacity of measurement chip, for example, might use four measurement chips each measuring signals for a quarter of the touch screen. If the capacity of each measurement chip stays the same, large screens may require a very large number of measurement chips.

SUMMARY

p-0007The devices and processing techniques, discussed by way of examples below, allow multiple measurement devices or chips to work together to sample a screen that is larger than one measurement device might sample, by allowing sharing of the X or drive lines amongst the measurements devices. Particular examples described in this specification can be implemented so as to realize one or more of the following optional advantages. The sharing of the drive lines may allow for a screen sized or otherwise configured to have more measurement nodes than would be produced by the sum of those that could be measured by the individual devices. For a screen that requires multiple measurement devices, the drive line sharing thus may allow use of a smaller number of measuring devices.

BRIEF DESCRIPTION OF THE DRAWINGS

p-0008The drawing figures depict one or more implementations in accordance with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements.

p-0009<figref idrefs="DRAWINGS">FIG. 1</figref> illustrates an example of a large touch screen comprising four smaller screens or touch panel areas and associated measurement circuits or control units, where a number of the control units for measuring capacitance share the drive (X) lines;

p-0010<figref idrefs="DRAWINGS">FIG. 2</figref> schematically illustrates an example of an apparatus for detecting a touch;

p-0011<figref idrefs="DRAWINGS">FIG. 3</figref> illustrates an example of time that may be required to charge and discharge the apparatus of <figref idrefs="DRAWINGS">FIG. 2</figref>;

p-0012<figref idrefs="DRAWINGS">FIG. 4</figref> illustrates an example of changes in an electric field when a finger is present;

p-0013<figref idrefs="DRAWINGS">FIG. 5A</figref> illustrates an example of time that may be required to charge and discharge the apparatus of <figref idrefs="DRAWINGS">FIG. 2</figref>, when there is no touch;

p-0014<figref idrefs="DRAWINGS">FIG. 5B</figref> illustrates an example of time that may be required to charge and discharge the apparatus of <figref idrefs="DRAWINGS">FIG. 2</figref>, when there is a touch;

p-0015<figref idrefs="DRAWINGS">FIG. 6</figref> illustrates schematically an example of a basic measurement circuit;

p-0016<figref idrefs="DRAWINGS">FIG. 7</figref> illustrates schematically an example of a touch screen comprising a plurality of nodes and a control circuit for sensing position of a touch;

p-0017<figref idrefs="DRAWINGS">FIG. 8</figref> schematically illustrates a large touch screen comprising four smaller screens or touch panel areas, with one control unit measuring capacitance at the nodes of each of the four smaller screens or touch panel areas;

p-0018<figref idrefs="DRAWINGS">FIG. 9</figref> schematically illustrates an example of a large touch screen and measurement circuit where a number of control units for measuring capacitance share the drive (X) lines;

p-0019<figref idrefs="DRAWINGS">FIG. 10</figref> illustrates schematically in more detail the example of a large touch screen having a number of screens or touch panel areas;

p-0020<figref idrefs="DRAWINGS">FIG. 11</figref> illustrates schematically an example of a connection of a panel or a portion thereof to a control unit;

p-0021<figref idrefs="DRAWINGS">FIG. 12</figref> illustrates schematically in more detail the example of a connection of a panel to a control unit;

p-0022<figref idrefs="DRAWINGS">FIG. 13</figref> illustrates an example of a method for combining control units for coordinated measurements on a large touch screen using drive line sharing; and

p-0023<figref idrefs="DRAWINGS">FIG. 14</figref> illustrates another example of a method for combining control units for coordinated measurements on a large touch screen using drive line sharing.

DETAILED DESCRIPTION

p-0024In the following detailed description, numerous specific details are set forth by way of examples in order to illustrate the relevant teachings. In order to avoid unnecessarily obscuring aspects of the present teachings, those methods, procedures, components, and/or circuitry that are well-known to one of ordinary skill in the art have been described at a relatively high-level.

p-0025Reference now is made in detail to the examples illustrated in the accompanying figures and discussed below. <figref idrefs="DRAWINGS">FIG. 1</figref> schematically illustrates an example of a touch responsive position sensor. The sensor includes a screen or panel <b>1</b> for sensing touch and associated circuitry for driving and sensing lines of the screen to detect a touch and position of the touch on the screen <b>1</b>.

p-0026In this first simple example, the overall touch screen <b>1</b> is formed of a 2×2 matrix of smaller touch screen areas <b>2</b>. As such, the exemplary screen <b>1</b> includes four touch screen regions or areas <b>2</b>A to <b>2</b>D. The touch screen <b>1</b> has an array of sensing nodes formed at intersections of drive lines (horizontal X lines in the illustrated orientation) and sense lines (vertical Y lines in the illustrated orientation). A number of such nodes are included within each of the four touch screen regions or areas <b>2</b>A to <b>2</b>D. The X (drive) lines extend across all Y sense lines, for example, across both of the touch screen areas at the corresponding Y axis value. Similarly, the Y lines extend across all of the X lines, for example, across both of the touch screen areas at the corresponding X axis value.

p-0027If the screens were physically separated, they would be physically and electrically connected to form the larger panel. As part of the electrical connection, each line would be connected from one screen to a corresponding line in the next adjacent screen in the appropriate X or Y direction. If the screens are logically separate, that is to say regions or areas of a continuous larger screen, then the lines could run continuously across the regions forming the overall screen, in the respective X and Y directions.

p-0028The exemplary system for sensing touch and touch position on the screen <b>1</b> includes a number of control units. However, there are fewer control units than there are touch sensing areas <b>2</b> of the matrix of the touch screen <b>1</b>. In the 2×2 matrix example of <figref idrefs="DRAWINGS">FIG. 1</figref>, there are two control units <b>3</b>A and <b>3</b>B. The system or device may also include a master control represented by the processor <b>4</b> in the example. A number of the X drive lines <b>5</b> connect to each of the control units <b>3</b>A and <b>3</b>B; and a number of the Y sense lines <b>6</b> connect to each of the control units <b>3</b>A and <b>3</b>B. Each control unit includes or may be a measuring device for measuring one or more parameters of signals at a number of nodes of the array of the touch screen <b>1</b> to determine a touch at or in the vicinity of the individual nodes the measurement device senses.

p-0029The processor <b>4</b> serving as the master control connects to the control units <b>3</b>A, <b>3</b>B via data leads <b>7</b>. The processor <b>4</b>, for example, processes touch detection data from the control units to identify the node or nodes at which touch is detected on the overall area of screen <b>1</b>, based on timing of X line drive and sense line detection. Based on the node or nodes at which touch is detected, the processor <b>4</b> determines the position of each touch detected on the screen <b>1</b>. The processor <b>4</b> may also provide control signals to the control units <b>3</b>A and <b>3</b>B over the data leads <b>7</b>. In the example, the processor <b>4</b> also provides a higher level interface of the touch responsive position sensor to a system or device that uses the touch input information, for example, to a processor of a computer, personal digital assistant or mobile station.

p-0030The example uses only two control units <b>3</b>A and <b>3</b>B. Screens having more areas, lines and/or sensing nodes at the line intersections would use a larger number of control units; and examples of such screens and the attendant configuration control units are discussed later.

p-0031The example of <figref idrefs="DRAWINGS">FIG. 1</figref> implements drive line sharing. Hence, each set of the drive lines is driven by only one measurement device/control unit, but all of the drive lines are shared across multiple measurement devices for sensing purposes. Each individual X line is driven by only one control unit, but all of the measurement devices sense signals at some number the nodes on the particular X line. However, any one measurement device senses signals at nodes via only an appropriate number or subset of the sense lines connected to the measurement device.

p-0032Each of the control units <b>3</b>A and <b>3</b>B drives and senses only the respective number of lines of each type within its design capacity. However, because the X drive lines extend across all Y sense lines, the X lines are shared by both of the control units <b>3</b>A and <b>3</b>B, in this first example. Each unit drives only the appropriate number of X lines. However, by synchronizing timing of the operations of the control units across the vertical sets of regions/lines (across the drive lines in the set of regions <b>2</b>A-<b>2</b>B and in the set of regions <b>2</b>C-<b>2</b>D), it becomes possible for each of the control units to sense touch at the Y lines that the respective unit connects to even when there is a touch at a crossing of an X line driven by the other control unit. In this way, the control units can work together to sample signals at the various nodes of a large screen <b>1</b> by the sharing of the X (drive) lines.

p-0033Hence, to facilitate the touch position detection, the control units <b>3</b>A and <b>3</b>B are synchronized. One or more of the drive (X) lines of each control unit may be used to synchronize the control units. In another example, the hardware of the control unit is configured to provide a separate synchronization component, freeing up all the drive (X) lines for actual use in touch sensing cycles. In another example, synchronization of the control units <b>3</b>A, <b>3</b>B, may be provided by the processor <b>4</b> via data lines <b>7</b>.

p-0034In this way, each measurement device or control unit <b>3</b>A or <b>3</b>B is configured to drive a first number of but not all of the X drive lines <b>5</b> extending across at least two of the sensing areas in the first direction. Each measurement device or control unit <b>3</b>A or <b>3</b>B also is configured to sense signals relating to a touch at nodes of intersection with all of the X drive lines <b>5</b>, via a second number of but not all of the sense lines <b>6</b> extending across at least two of the sensing areas <b>2</b>A-<b>2</b>C or <b>2</b>B-<b>2</b>D in the second direction. The measurement devices or control units <b>3</b>A and <b>3</b>B are configured to operate synchronously in a manner to identify one or more nodes, from among all nodes in all of the touch sensing areas <b>2</b>A-<b>2</b>D of the matrix of the touch screen <b>1</b>, as indication(s) of a position of a detected touch of the screen.

p-0035With that overview of a simple example, it may be helpful to consider touch sensing operations in somewhat more detail and then discuss a more complex example of the touch sensing with drive line sharing amongst measuring devices. Specific examples of the methodology will be discussed after the more complex panel example.

p-0036<figref idrefs="DRAWINGS">FIG. 2</figref> schematically illustrates an example of an apparatus for detecting a touch. The apparatus includes a control unit <b>10</b> provided with three switches <b>12</b>, <b>16</b> and <b>18</b>. Control unit <b>10</b> may be provided as a single integrated circuit chip such as a general purpose microprocessor, a microcontroller, a programmable logic device/array, an application-specific integrated circuit (ASIC), or a combination thereof. Switch <b>12</b> is provided between VDD and ground and is also connected to a sensor <b>13</b>. The self coupling capacitance of the sensor <b>13</b> is C_X. The sensor <b>13</b> has two electrodes, an X (drive) electrode and a Y (sense) electrode. The apparatus measures the transverse coupling capacitance between the X and Y electrodes.

p-0037The sensor <b>13</b> is connected in series to a sampling capacitor <b>15</b> having a sampling capacitance C_S. The sampling capacitor <b>15</b> may have a sampling capacitance C_Swhich is considerably larger than the sensor capacitance C_X. In one example, the sampling capacitance C_Sis at least 1000 times larger than the sensor capacitance C_X, where the sensor capacitance C_Xmay be around 1 pF to 10 pF. The sampling capacitor <b>15</b> is also connected in series to the switches <b>16</b> and <b>18</b>, both of which are connected to ground.

p-0038Capacitance C is a measure of the amount of electric charge stored for a given electric potential.

p-0039<maths id="MATH-US-00001" num="00001"><math overflow="scroll"><mrow><mi>C</mi><mo>=</mo><mfrac><mi>Q</mi><mi>V</mi></mfrac></mrow></math></maths>

p-0040Where V is the voltage between the plates and Q is charge.

p-0041After opening switch <b>16</b>, a voltage pulse is applied to the apparatus, by adjusting switch <b>12</b> to connect the sensor <b>13</b> to VDD, followed by closing switch <b>18</b> which causes charge to flow through C_Xinto C_S, accumulating charge at C_Sand C_S. The sensor capacitance C_Xis then discharged, by, opening switch <b>18</b>, closing switch <b>16</b> and adjusting switch <b>12</b> to connect to ground. Since only the sensor capacitance C_Xis discharged after each voltage pulse, the capacitance C_Sheld at the sampling capacitor <b>15</b> is increased with each voltage pulse. This step wise increase is illustrated in <figref idrefs="DRAWINGS">FIG. 3</figref>, where V_CSis the voltage accumulated at the sampling capacitor <b>15</b>.

p-0042A predetermined number of voltage pulses is applied to the apparatus. After the predetermined number of pulses is applied to the apparatus, the capacitance C_Saccumulated in the sampling capacitor <b>15</b> is discharged. The time taken for the capacitance to discharge to a reference voltage is measured.

p-0043As illustrated in <figref idrefs="DRAWINGS">FIG. 4</figref>, when a stylus or a user's finger <b>19</b>, which has a touch capacitance to Earth C_t, is moved close to (or contacts) the sensor <b>13</b>, the touch capacitance of the object diverts charge away from the drive electrode of C_Xto earth so that the capacitance C_Saccumulated in the sampling capacitor <b>15</b> with each voltage pulse is reduced. In one example, the sensor <b>13</b> is provided behind a dielectric panel so that the finger <b>19</b> does not directly contact the sensor <b>13</b>. In another example, or in addition to a dielectric panel, the finger <b>19</b> may be provided in close proximity to the sensor <b>13</b>, but not directly contacting the sensor <b>13</b>.

p-0044<figref idrefs="DRAWINGS">FIG. 5A</figref> illustrates the voltage V_CSaccumulated at the sampling capacitor <b>15</b> after the predetermined number of pulses when there is no touch, and the time required to discharge the sampling capacitor <b>15</b>. <figref idrefs="DRAWINGS">FIG. 5B</figref> illustrates the voltage V_CSaccumulated at the sampling capacitor <b>15</b> after the predetermined number of pulses when a user's finger <b>19</b> is close to or contacts the sensor <b>13</b> (i.e. when there is a touch), and the time required to discharge the sampling capacitor <b>15</b>. Since the sampling capacitor <b>15</b> is connected to the negative side of the sensor <b>13</b>, in the example of <figref idrefs="DRAWINGS">FIG. 2</figref>, the accumulated voltage V_CShas a negative value.

p-0045As can be seen from <figref idrefs="DRAWINGS">FIGS. 5A and 5B</figref>, the voltage V_CSaccumulated in <figref idrefs="DRAWINGS">FIG. 5B</figref> is reduced when compared to the voltage V_CSaccumulated in <figref idrefs="DRAWINGS">FIG. 5A</figref>. In addition, the time required to discharge the sampling capacitor <b>15</b> in <figref idrefs="DRAWINGS">FIG. 5B</figref> is reduced when compared to the time required to discharge the sampling capacitor <b>15</b> in <figref idrefs="DRAWINGS">FIG. 5A</figref>. The reduction in time required to discharge the sampling capacitor <b>15</b> in <figref idrefs="DRAWINGS">FIG. 5B</figref> indicates that there is a touch. The difference between the time required to discharge the sampling capacitor <b>15</b> when there is no touch (illustrated in <figref idrefs="DRAWINGS">FIG. 5A</figref>) and the time required to discharge the sampling capacitor when there is a touch (illustrated in <figref idrefs="DRAWINGS">FIG. 5B</figref>) is referred to as a delta.

p-0046The detection of a delta indicates a touch, because the delta indicates that there has been a change of charge accumulated at the sampling capacitor <b>15</b>, when compared to the amount of charge expected to be accumulated at the sampling capacitor <b>15</b> when there is no touch.

p-0047<figref idrefs="DRAWINGS">FIG. 6</figref> illustrates a basic circuit for measuring the magnitude of Vcs. The control unit <b>10</b> of <figref idrefs="DRAWINGS">FIG. 2</figref> includes a resistor <b>49</b>, switch <b>40</b>, a comparator <b>41</b>, a register <b>45</b>, a counter <b>43</b> and a clock signal <b>47</b>. The resistor <b>49</b>, comparator <b>41</b> and counter <b>43</b> are used to measure the magnitude of Vcs. The time required to discharge the sampling capacitor to a reference voltage is measured with the counter and the comparator, such that the counter value is the measurement.

p-0048As illustrated in <figref idrefs="DRAWINGS">FIG. 7</figref>, in order to create a touch sensitive position sensor screen having more than one touch sensor <b>13</b>, a plurality of drive and sense electrodes can be provided to create an array of sensing elements <b>220</b> (touch sensors <b>13</b>) within a panel <b>210</b> of the position sensor. The drive electrodes (X) form one plate of each sensor <b>13</b> and the sense (Y) electrodes form the other plate of each sensor <b>13</b> having a capacitance C_X. The position sensor also includes a plurality of resistors <b>230</b>, which may have different values, and a control unit <b>10</b>. <figref idrefs="DRAWINGS">FIG. 7</figref>, illustrates one exemplary matrix of eight sensing elements <b>220</b>, however many other configurations are possible.

p-0049The basic measuring circuit illustrated in <figref idrefs="DRAWINGS">FIG. 6</figref> and described above is provided as an example only. Other methods of measuring a touch can be used.

p-0050The matrix of drive and sense electrodes forms a two-dimensional position sensor capable of sensing the position of a touch on the panel <b>210</b>. The control unit <b>10</b> uses a scanning sequence through the rows of drive electrodes and the columns of sense electrodes to measure coupling capacitance at the intersections or nodes. Examples of position sensors include touch screens and touch pads, which can be provided attached to or as part of computers, personal digital assistants (PDA), satellite navigation devices, mobile phones, portable media players, portable game consoles, public information kiosks, and point of sale systems etc. Position sensors can also be used as control panels on various appliances.

p-0051<figref idrefs="DRAWINGS">FIG. 8</figref> illustrates schematically four touch sensitive screens or regions, <b>50</b>A, <b>50</b>B, <b>50</b>C and <b>50</b>D, each having an array of sensing elements, arranged to create a large touch sensitive screen <b>500</b>. Each of the screens or regions <b>50</b>A to <b>50</b>D is connected to a respective control unit <b>520</b>A to <b>520</b>D. Each control unit <b>520</b>A to <b>520</b>D drives the X electrode lines <b>550</b> of its respective screen <b>50</b>A to <b>50</b>D and samples the Y electrode lines <b>540</b> of its respective screen <b>50</b>A to <b>50</b>D. Therefore, each control unit <b>520</b>A to <b>520</b>D forms a measuring device capable of detecting a touch and the position thereof on its respective screen <b>50</b>A to <b>50</b>D which makes up a part of (a quarter in <figref idrefs="DRAWINGS">FIG. 8</figref>) the overall screen <b>500</b>. Each control unit may be formed of a separate chip. In the arrangement of <figref idrefs="DRAWINGS">FIG. 8</figref>, each screen is logically or physically separated. In contrast to <figref idrefs="DRAWINGS">FIG. 1</figref>, the X lines and Y lines of <figref idrefs="DRAWINGS">FIG. 8</figref> do not extend across the entire screen <b>500</b>. Each screen <b>50</b>A-<b>50</b>D has its own X lines and Y lines connected to its own control unit <b>520</b>A to <b>520</b>D.

p-0052Each control unit <b>520</b>A to <b>520</b>D drives and senses signals at nodes within the area <b>50</b>A to <b>50</b>D that it controls. In such an arrangement, the X lines may extend only across the region controlled by the respective unit. For example, the X drive lines <b>550</b> connected to the first control unit <b>520</b>A extend only across the first screen or area <b>50</b>A. Similarly, the X drive lines <b>550</b> connected to the second control unit <b>520</b>B extend only across the second screen or area <b>50</b>B. The X drive lines <b>550</b> connected to the third control unit <b>520</b>C extend only across the third screen or area <b>50</b>C; and the X drive lines <b>550</b> connected to the fourth control unit <b>520</b>D extend only across the second screen or area <b>50</b>D. Similarly, the sense lines extend only across the region controlled by the respective unit. Such an arrangement works much as if the areas <b>50</b>A to <b>50</b>D are actually separate screens.

p-0053Each control unit <b>520</b>A to <b>520</b>D is only capable of driving and sensing a predetermined number of nodes, which limits the number of nodes in each respective screen or region <b>50</b>A to <b>50</b>D. For example, each screen or area might have 10 X lines and 10 Y lines, and each control unit would be capable of driving/sensing 100 nodes. In another example, each screen might have 16 X lines and 14 Y lines, and each control unit would be capable of driving/sensing 224 nodes. Therefore in order to create and measure signals at nodes of a large touch screen <b>500</b>, such as illustrated in <figref idrefs="DRAWINGS">FIG. 8</figref>, four times the size of a touch screen compatible with a single control unit chip of a particular capacity, having four times the number of nodes present in such a touch screen, four control units <b>520</b>A to <b>520</b>D are required in order to drive the large touch screen <b>500</b>.

p-0054In order to create a large touch screen <b>500</b>, for example nine times the size of a touch screen compatible with a single control unit chip of a particular capacity (e.g. a 3×3 touch screen), nine control units would be required. Furthermore, in order to create a large touch screen <b>500</b>, for example sixteen times the size of the basic touch screen unit (e.g. a 4×4 touch screen), sixteen control units would be required. Consequently, very large touch screens require very large numbers of control units.

p-0055<figref idrefs="DRAWINGS">FIG. 9</figref> illustrates an example of an alternative arrangement for creating a large touch sensitive screen by using shared X (drive) lines to enable drive/sensing of the larger number of nodes without necessarily requiring so many control units. The X (drive) lines are shared in that they extend across all Y sense lines of the screen connected to all of the control units <b>520</b>A to <b>520</b>C. The exemplary large touch screen <b>500</b> of <figref idrefs="DRAWINGS">FIG. 9</figref> has nine individual touch screens or touch screen areas of the particular unit size in a 3×3 matrix arrangement. In the arrangement of <figref idrefs="DRAWINGS">FIG. 9</figref>, the control units have been combined, so that fewer control units are required. The control units of <figref idrefs="DRAWINGS">FIG. 9</figref> work together to sample the large screen <b>500</b> by sharing the X (drive) lines.

p-0056<figref idrefs="DRAWINGS">FIG. 10</figref> illustrates the screen <b>500</b> of <figref idrefs="DRAWINGS">FIG. 9</figref> in further detail. As can be seen from <figref idrefs="DRAWINGS">FIG. 10</figref>, the large screen <b>500</b> is divided into nine touch screen areas <b>50</b>A to <b>50</b>I each of a size (e.g. number of nodes) corresponding to the capacity of one control unit. In an arrangement, such as illustrated in <figref idrefs="DRAWINGS">FIG. 8</figref>, a separate control unit would measure signals from nodes in each screen area <b>50</b>A to <b>50</b>I. However, the arrangement of <figref idrefs="DRAWINGS">FIG. 9</figref> enables each X line driven by one of the control units <b>520</b>A, <b>520</b>B, <b>520</b>C to be sampled by the Y lines of all of the control units <b>520</b>A, <b>520</b>B, <b>520</b>C. This allows for a screen size which is the sum of the X lines of all the control units times the sum of the Y lines of all the control units, but requiring fewer control units. In the arrangement of <figref idrefs="DRAWINGS">FIG. 8</figref>, it was not possible to sense signals at nodes along the X lines controlled by a first control unit with the Y lines of another control unit. Consequently, it would not be possible to detect screens <b>10</b>A, <b>10</b>B, <b>10</b>D, <b>10</b>F, <b>10</b>H and <b>10</b>I, since these combinations of X and Y lines would not exist.

p-0057The control units <b>520</b>A, <b>520</b>B and <b>520</b>C are synchronized. In one example, at least one of the drive (X) lines of each control unit is used to synchronize the control units. In the example where a control unit is capable of driving/sensing 224 nodes, five of the X lines are used for synchronization, resulting in each screen area <b>50</b> having 11 X lines and 14 Y lines. In another example, the hardware of the control unit is configured such that a separate synchronization component is provided, freeing up all the drive (X) lines for sensing. In another example, synchronization of the control units may be provided by a processor <b>530</b>, the processor <b>530</b> providing control signals <b>560</b> to each of the control units <b>520</b>A, <b>520</b>B, <b>520</b>C.

p-0058<figref idrefs="DRAWINGS">FIG. 13</figref> illustrates one method of detecting a touch using the arrangement of <figref idrefs="DRAWINGS">FIG. 9</figref>. As indicated in <figref idrefs="DRAWINGS">FIG. 13</figref>, the process is initiated at step <b>300</b>. At step <b>305</b> it is determined at each control unit <b>520</b>A, <b>520</b>B and <b>520</b>C whether that control unit is ready to begin sensing. If the control unit is not ready then the process waits until the unit is ready. When the control unit is ready, it sends a ready signal to each of the other control units at step <b>310</b>. At step <b>315</b> it is determined whether the control unit has received a ready signal from all of the other control units in the system. If not, then the system waits until each control unit has received a ready signal from all of the other control units in the system. If a ready signal has been received from all of the other control units in the system, then the control units have been synchronized and are ready to begin sensing. The control units are synchronized before each sampling.

p-0059At step <b>320</b> sampling is initiated. At step <b>325</b> each X line is sampled using the Y lines associated with all the control units in the system. At any point in time, one control unit drives the X lines in the set connected to that unit. The control units that are not driving the X lines connected to those units at any given point in time provide a dummy sample, so that the X lines of the one control unit can be sampled by all the Y lines of all of the control units in the system.

p-0060Data signals <b>560</b> from each control unit <b>520</b>A, <b>520</b>B and <b>520</b>C are transferred to a processor <b>530</b> at step <b>330</b>. The processor <b>530</b> is provided for sensing a touch or a proximity of an object and determining its position on the overall screen based on the received sense signals. At step <b>335</b>, the processor <b>530</b> processes all the data received from all of the control units <b>520</b>A, <b>520</b>B and <b>520</b>C and determines if there has/has not been a touch at the touch screen <b>500</b>. A processor <b>530</b> is used to process the data since each control unit <b>520</b>A, <b>520</b>B and <b>520</b>C is not aware of the data produced by the other control units <b>520</b>A, <b>520</b>B and <b>520</b>C. If a processor <b>530</b> was not used to process the data, then error readings would result at the edge of each screen area <b>50</b>A to <b>50</b>I. The processor <b>530</b> receives data from all the control unit <b>520</b>A, <b>520</b>B and <b>520</b>C so is able to eliminate nonlinearities at the screen area <b>50</b>A to <b>50</b>I boundaries.

p-0061The processor <b>530</b> may be any known processor, such as a microcontroller, microprocessor or central processor.

p-0062The processor <b>530</b> is connected to an interface <b>570</b>, which connects to the device in which the touch screen is provided.

p-0063In another example, the processor <b>530</b> is not required. Each control unit <b>520</b>A, <b>520</b>B, <b>520</b>C may be provided with its own processor. In such an example, it is possible for all the data to be transferred to one of the control units <b>520</b>A, <b>520</b>B or <b>520</b>C for processing at that control unit <b>520</b>A, <b>520</b>B or <b>520</b>C. The data from all of the control units <b>520</b>A, <b>520</b>B, <b>520</b>C is processed together at one of the control unit <b>520</b>A, <b>520</b>B or <b>520</b>C to eliminate nonlinearities at the screen area <b>50</b>A to <b>50</b>I boundaries.

p-0064<figref idrefs="DRAWINGS">FIG. 14</figref> illustrates another method of detecting a touch using the arrangement of <figref idrefs="DRAWINGS">FIG. 9</figref>. As indicated in <figref idrefs="DRAWINGS">FIG. 14</figref>, the process is initiated at step <b>400</b>. At step <b>405</b> it is determined whether all of the control units <b>520</b>A, <b>520</b>B and <b>520</b>C have been synchronized. If all of the control units <b>520</b>A, <b>520</b>B and <b>520</b>C have not been synchronized, then the process waits for the control units <b>520</b>A, <b>520</b>B and <b>520</b>C to have been synchronized. If all of the control units <b>520</b>A, <b>520</b>B and <b>520</b>C have been synchronized, then the process moves on to step <b>410</b>. At step <b>410</b> sampling is initiated. At step <b>415</b> each X line is sampled using the Y lines associated with all the control units in the system. The control units that are not driving the X lines at any given point in time provide a dummy sample, so the X lines of one control unit can be sampled by all the Y lines of all of the control units in the system.

p-0065Data signals <b>560</b> from each control unit in the system are transferred to a processor <b>530</b> at step <b>420</b>. Finally at step <b>425</b>, the processor <b>530</b> processes all the data received from all of the control units <b>520</b>A, <b>520</b>B and <b>520</b>C and determines if there has/has not been at touch at the touch screen <b>500</b>.

p-0066The process of <figref idrefs="DRAWINGS">FIG. 14</figref> can be utilized, for example, when a separate synchronization component is provided, or when the processor <b>530</b> controls synchronization of the control units <b>520</b>A, <b>520</b>B, <b>520</b>C. The process of <figref idrefs="DRAWINGS">FIG. 14</figref> can also be utilized, for example, when each control unit <b>520</b>A, <b>520</b>B, <b>520</b>C is provided with its own processor. In such an example, all the data would be transferred to one of the control units <b>520</b>A, <b>520</b>B or <b>520</b>C for processing at that control unit <b>520</b>A, <b>520</b>B or <b>520</b>C.

p-0067Although the examples of <figref idrefs="DRAWINGS">FIGS. 9 and 10</figref> were described with reference to a large touch screen <b>500</b>, having a 3×3 arrangements, the present subject matter may also be utilized to create a large touch screen <b>500</b> having a 2×2 arrangement like that of <figref idrefs="DRAWINGS">FIG. 1</figref>, requiring two control units; a 4×4 arrangement, requiring four control units; a 5×5 arrangement, requiring five control units etc. The drive line sharing technologies may also be utilized to create a large touch screen <b>500</b> having a 2×4 arrangement, 3×4 arrangement etc. as required. In such an arrangement, the touch screen would require four control units. The control units that are not driving the X lines, or Y lines as appropriate may provide a dummy sample instead.

p-0068<figref idrefs="DRAWINGS">FIG. 11</figref> illustrates schematically a panel <b>210</b> including a plurality of drive (X) electrode lines (not illustrated) connected to drive channels <b>280</b> and a plurality of sense (Y) electrode lines (not illustrated) connected to sense channels <b>240</b>. The drive channels <b>280</b> and the sense channels <b>240</b> are connected to a control unit <b>200</b> via a connector <b>270</b>. The connector <b>270</b> may be a conductive trace or a feed-through.

p-0069The control unit <b>200</b> includes a drive unit <b>120</b> for supplying drive signals to the drive electrodes, and a sense unit <b>140</b> for sensing signals from the sense electrodes. The control unit <b>200</b> thus controls the operation of the drive and sense units <b>120</b>, <b>140</b>. The control unit <b>200</b> may also include a storage device <b>180</b>, such as a computer readable medium.

p-0070Although the drive unit <b>120</b>, and sensing unit <b>140</b> are illustrated as separate components in <figref idrefs="DRAWINGS">FIG. 11</figref>, the functionality of these units may be provided in a single integrated circuit chip such as a general purpose microprocessor, a microcontroller, a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). In addition, a separate drive unit may be provided for each drive channel connected to each electrode.

p-0071As illustrated in <figref idrefs="DRAWINGS">FIG. 12</figref> the drive channels Xn, Xn+1, Xn+2, . . . Xn+m are connected to the drive unit <b>120</b>, although in one example, each drive channel is connected to a separate drive unit <b>120</b>. In addition, the sense channels Yn, Yn+1, Yn+2, . . . Yn+m are connected to the sense unit <b>140</b>.

p-0072In another example, not illustrated, separate drive and sense control units may be provided. In this instance, a drive control units may include a drive unit and a storage device, and a sense control units may include a sense unit and a storage device. If a large touch screen <b>500</b> having a 2×4 arrangement etc. is provided, then it may be advantageous to use two drive control units and four sense control units etc.

p-0073The above examples show that the drive line sharing approach provides an efficient technique to scale the electronics to measure more nodes on larger touch panels. The first example used two control units to perform drive and sensing on a 2×2 matrix touch panel. The second example used three control units to perform drive and sensing on a 3×3 matrix touch panel. A similar approach can be used for larger and larger square matrix panels, with one additional control unit/measuring device for each additional row/column. However, those skilled in the art will recognize that the shared drive line strategy to scaling the number of control units also may be adapted to panel configurations that utilize different numbers of screens or areas in the different panel dimensions. For example, each control unit might handle less than its full capacity of drive or sense lines but handle its full capacity of the other type of lines. Alternatively, one controller might only drive a set of X lines for a row of regions or only sense a set of Y lines for a column of regions.

p-0074The position sensors described above can be attached to numerous electronic devices, such as computers, personal digital assistants (PDA), satellite navigation devices, mobile phones, portable media players, portable game consoles, public information kiosks, point of sale systems etc. These electronic devices may include a central processor or other processing device for executing program instructions, an internal communication bus, various types of memory or storage media (RAM, ROM, EEPROM, cache memory, disk drives etc.) for code and data storage, and one or more network interface cards or ports for communication purposes.

p-0075Various modifications may be made to the examples and embodiments described in the foregoing, and any related teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings.